[][Backport napi releated bug fixes to openwrt 21.02]

[Description]
Add some napi releated bug fixeds to openwrt 21.02
Please refer to following patches for detail:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/net/core/dev.c?id=0315a075f1343966ea2d9a085666a88a69ea6a3d
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/net/core/dev.c?id=3765996e4f0b8a755cab215a08df744490c76052
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/net/core/dev.c?id=719c571970109b0d0af24745d31b202affc9365f

Please notice following changed:
+               new &= ~(NAPIF_STATE_THREADED | NAPIF_STATE_PREFER_BUSY_POLL);
/* No "NAPIF_STATE_PREFER_BUSY_POLL" in kernel 5.4 */
-       clear_bit(NAPI_STATE_PREFER_BUSY_POLL, &n->state);

Test: Build PASS

[Release-log]
N/A

Change-Id: Icb0d352821fb91108eb08f46f8bda8f1419f7777
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6050622
3 files changed